This invention relates to a sensing device for detecting the contacting of a moving element with any fixed body, more particularly to a sensing device which can effectively prevent damages on a moving element such as a robot arm which may occur when the element comes into contact with a fixed body.
In case a robot 1 shown in FIG. 1 serves in a welding operation, a welding torch 2 attached to the distal end of the robot arm may come into contact with a work piece or jigs by accident. Such contact accident may be caused by the inaccuracy of the size of the work, the inaccuracy in positioning of the work, or errors in the arm-handling operaion. In such a case, depending on the degree of contact or collision, the welding torch 2 suffers deformation or ruptures, and in the worst case, the robot arm per se is damaged.
In general, when such contact accident occurs, as one of the countermeasures, the operation of the robot is stopped. As another countermeasure, the robot may be provided with means for protecting the arm wrist. For example, as shown in FIG. 2, such arm wrist protecting means may be constructed by interposing a bakelite ring 5 having poor strength against rupture between a support member 3 and a work-side member 4 such as a torch-holder and fastening the bakelite ring 5 therebetween with set screws 6. Due to such construction, when a contact accident occurs, the bakelite ring 5 ruptures thus preventing the influence of the contact accident to the main robot elements.
In the above method, however, since the robot per se is not provided with any sensing ability, the robot continues the movement thereof without performing the required or normal operation until an operator finds out about the rupture of the bakelite ring 5. Furthermore, when the bakelite ring 5 ruptures, the ring must be replaced with a new bakelite ring 5. This implies that the robot must again be provided with a teaching of the programmed operation after repair to resume the programmed operation.
Accordingly, it is an object of the present invention to provide a contact sensing device which can accurately and readily detect the contacting of a work-side member which is mounted on the robot arm or a moving element of any other machines with a fixed body including the work.